$-7bc + 7c + 6d - 4 = 6c - 7d - 6$ Solve for $b$.
Solution: Combine constant terms on the right. $-7bc + 7c + 6d - {4} = 6c - 7d - {6}$ $-7bc + 7c + 6d = 6c - 7d - {2}$ Combine $d$ terms on the right. $-7bc + 7c + {6d} = 6c - {7d} - 2$ $-7bc + 7c = 6c - {13d} - 2$ Combine $c$ terms on the right. $-7bc + {7c} = {6c} - 13d - 2$ $-7bc = -{c} - 13d - 2$ Isolate $b$ $-{7}b{c} = -c - 13d - 2$ $b = \dfrac{ -c - 13d - 2 }{ -{7c} }$ Swap the signs so the denominator isn't negative. $b = \dfrac{ {1}c + {13}d + {2} }{ {7c} }$